Two systems are being investigated to understand, on a molecular level, the role of protein-nucleic acid interactions in gene expression. Using QBeta replicase (an enzyme induced by infecting E. coli with QBeta RNA bacteriophage) and the various RNA species which it will utilize as templates for replication in vitro, we plan to elucidate the molecular basis of template specificity and to determine which aspects of RNA primary, secondary, or tertiary structure as well as which replicase subunits are functionally important in the various steps of RNA replication--binding, initiation of synthesis, elongation, and separation of product from template strand. The second area of investigation is the regulation of selective transcription by the interaction of DNA-dependent RNA polymerase with DNA promoters. Our aim is to understand the control of transcription by elucidating the required conformation and conformational changes which occur in both the DNA promoter region and the RNA polymerase during promoter site selection and RNA chain initiation. The modulations of the transient conformations by changes in the environment, DNA sequence and protein modifications are also being investigated.